1. Field of the Invention
This invention relates to semiconductive alloys made from silicon germanium. More specifically, the invention is a silicon germanium semiconductive alloy that can be fabricated in relatively thick layers without defects and dislocations.
2. Description of the Related Art
Silicon germanium (SiGe) is an important semiconductive alloy used in Field Effect Transistors (FETs), High Electron Mobility Transistors (HEMTs), Hetero Bi-polar Transistors (HBTs), Thermo-Electric (TE) devices, photovoltaic solar cells, and photon detectors. Typically, SiGe is grown on common silicon water substrates. However, the growth of thick (i.e., greater than tens of nanometers), high-quality (i.e., defect free) SiGe layers on a silicon substrate is difficult because SiGe has a larger lattice constant than silicon. This means that the SiGe layers close to the silicon substrate are strained while severe defects (e.g., micro twins, cracks, delaminations, etc.) develop in the layers of SiGe that exceed the critical thickness of tens of nanometers because of the lattice mismatch. Thus, at best, only strained SiGe layers with very thin thicknesses (i.e., less than tens of nanometers) are utilized for high-quality electronic device fabrication.